Discrete Mathematics Lecture Notes
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Questions and Answers

What does the matrix MR represent?

  • A relation from set B to set A
  • A relation from set A to set B (correct)
  • A function of set A
  • A relation between two different sets

Which of the following ordered pairs is included in the set R derived from matrix MR?

  • (a2, b1)
  • (a1, b4) (correct)
  • (a3, b2)
  • (a2, b4)

What is the relationship between MR and MR−1?

  • MR is the transpose of MR−1
  • MR−1 is the transpose of MR (correct)
  • MR is the inverse of MR−1
  • MR and MR−1 are equal

In the context of a directed graph representation, what do the arrows represent?

<p>The direction of the relation (B)</p> Signup and view all the answers

Given the relation from A to B, how would you represent no relation from an element a1 to b2 in the matrix MR?

<p>0 (D)</p> Signup and view all the answers

How many elements would the digraph of relation R have based on the set A = {a1, a2, a3}?

<p>3 vertices (C)</p> Signup and view all the answers

What is the structure of MR if the relation contains no connections?

<p>All values are 0 (C)</p> Signup and view all the answers

What type of relation is represented if there are arrows going from one vertex to multiple vertices in a digraph?

<p>One-to-many relation (B)</p> Signup and view all the answers

What is the correct notation to denote that an element 'a' is part of set A?

<p>a ∈ A (A)</p> Signup and view all the answers

How are sets denoted in mathematical notation?

<p>With upper case letters (B)</p> Signup and view all the answers

In set theory, what is the significance of the order of elements in a set?

<p>The order is irrelevant when defining a set (A)</p> Signup and view all the answers

Which notation is used to indicate that a certain condition is met by members of a set?

<p>Predicate Notation (B)</p> Signup and view all the answers

Which of the following correctly represents a set of prime numbers less than 10?

<p>{2, 3, 5, 7} (A)</p> Signup and view all the answers

What is the correct description of the symbols '∈' and '∉'?

<p>'∈' indicates membership and '∉' indicates non-membership (C)</p> Signup and view all the answers

In the context of set theory, what does the universal set refer to?

<p>A set containing all elements in a particular context (C)</p> Signup and view all the answers

What are the correct symbols for the set containing only the even numbers?

<p>{2n | n ∈ Z} (C)</p> Signup and view all the answers

What is the domain of the relation R defined from A = {1, 2, 3, 4} to B = {x, y, z}?

<p>{1, 3, 4} (A)</p> Signup and view all the answers

What is the range of the relation R defined from A = {1, 2, 3, 4} to B = {x, y, z}?

<p>{y, z, x} (B)</p> Signup and view all the answers

How is the relation R represented in matrix form?

<p>MR = [[1, 1, 0], [0, 1, 1], [1, 0, 0], [0, 1, 0]] (C)</p> Signup and view all the answers

What is the inverse relation R −1 of R, given R = {(1, y), (1, z), (3, y), (4, x), (4, z)}?

<p>(y, 1), (z, 1), (y, 3), (x, 4), (z, 4) (B)</p> Signup and view all the answers

Which of the following correctly describes the notation MR for a relation?

<p>MR = [[mij]] represents a matrix where mij = 0 if (ai, bj) ∉ R (D)</p> Signup and view all the answers

If the matrix MR of a relation contains only 1s, what does this imply about the relation?

<p>Every element of the domain relates to every element of the codomain. (B)</p> Signup and view all the answers

Which of the following sequences is a solution to the recurrence relation $a_n = 8a_{n-1} - 16a_{n-2}$?

<p>$a_n = 1$ (A), $a_n = 0$ (D)</p> Signup and view all the answers

What initial conditions would define the recurrence relation for deeper population growth in this model?

<p>$d_0 = 1000$, $d_1 = 1100$ (A)</p> Signup and view all the answers

How much will be in the account after 100 years with a 9% interest compounded annually on an initial deposit of $1000?

<p>$1000(1.09)^{100}$ (A)</p> Signup and view all the answers

What will be the world's population in 2050 if it is currently 6 billion and grows at a rate of 1.3% per year?

<p>$6(1.013)^{30}$ (B)</p> Signup and view all the answers

Which of the following is not a characteristic of linear homogeneous recurrence relations?

<p>They can include non-homogeneous terms. (C)</p> Signup and view all the answers

What is the first term of the deeper population growth after one time period given the initial condition?

<p>1100 (A)</p> Signup and view all the answers

For the growth rate derived from a 10% increase per time period, which equation describes the population at time n?

<p>$d_n = (1.1)^n d_0$ (A)</p> Signup and view all the answers

Which expression correctly represents the amount in the account after n years with a principal $P$ at an interest rate $r$?

<p>$A = P(1 + r)^n$ (A)</p> Signup and view all the answers

Is the relation R = {(a, a), (b, b), (c, b), (d, d)} transitive?

<p>Yes, it is transitive. (D)</p> Signup and view all the answers

Which of the following properties must hold true for a relation to be an equivalence relation?

<p>Reflexive, symmetric, and transitive. (C)</p> Signup and view all the answers

What can be inferred if a relation R is reflexive and antisymmetric but not transitive?

<p>R is a partial order. (A)</p> Signup and view all the answers

Given the relation R = {(a, a), (b, c), (c, b), (d, d)}, is R transitive?

<p>No, because (b, b) is not present. (B)</p> Signup and view all the answers

In the set {1, 2, 3, 4}, which relation can be reflexive, symmetric, and not transitive?

<p>R = {(1,1), (2,2), (3,3), (1,2), (2,1), (3,4)} (D)</p> Signup and view all the answers

Which task must necessarily be completed before turning on the flash unit?

<p>Remove the lens cap. (A)</p> Signup and view all the answers

For the relation R = {(a, a), (b, b), (c, b), (d, d)}, which property does it not satisfy?

<p>It is symmetric. (D)</p> Signup and view all the answers

What characteristic is not required for a partial order?

<p>Symmetry. (C)</p> Signup and view all the answers

Study Notes

Expected Learning Outcomes

  • Ability to explain, solve and apply logical relationships.
  • Competence in using sets and relations to solve problems.
  • Familiarity with properties of numbers, relations, and functions in problem-solving.
  • Understanding and applying inclusion and exclusion principles.
  • Skills to resolve problems related to elementary graph theory.

Set Theory

  • A set is a well-defined collection of objects or numbers, denoted by uppercase letters.
  • Elements of a set are denoted by lowercase letters, represented in curly brackets (e.g., A = {a, b, c}).
  • Membership of an element in a set is indicated using ∈ (e.g., a ∈ A) or ∉ (e.g., x ∉ A).

Specifying a Set

  • List Notation: Members are listed in curly brackets (e.g., C = {Kshs, USD, Euro, Pound}). Order of elements is irrelevant.
  • Predicate Notation: Specifies sets based on shared conditions, useful when complete membership is unknown.

Representation of Relations

  • Relations between two sets A and B can be expressed using a matrix, where the entry is 1 if an ordered pair belongs to the relation and 0 if not.
  • For sets A and B, the matrix ( M_R ) is an ( m \times n ) grid where ( m ) and ( n ) are the number of elements in sets A and B, respectively.

Matrix Representation Example

  • Given A = {1, 2, 3} and B = {r, s}, the relation R defined by ( R = {(1, r), (2, s), (3, r)} ) has the matrix representation: [ M_R = \begin{pmatrix} 1 & 0 \ 0 & 1 \ 1 & 0 \end{pmatrix} ]

Undirected Graph Representation

  • Relations can be depicted as directed graphs (digraphs) by drawing circles for each element and using arrows to show connections based on the relation.

Transitive Relations

  • A relation is transitive if whenever it contains pairs (a, b) and (b, c), it must also contain (a, c).
  • Examples provided to discern transitive properties in relations.

Equivalence Relations

  • An equivalence relation is reflexive (every element relates to itself), symmetric (if a relates to b, then b relates to a), and transitive.
  • A partial order is reflexive, antisymmetric (if a relates to b and b relates to a, then a must be equal to b), and transitive.

Exercises

  • Tasks include providing specific examples of relations based on defined properties (reflexive, symmetric, transitive) and interpreting digraphs.

Linear Homogeneous Recurrence Relation

  • Defined as ( a_n = c_1 a_{n-1} + c_2 a_{n-2} + \ldots + c_k a_{n-k} ) for constants ( c_i ).
  • Examples illustrate how to formulate a recurrence relation based on a given scenario, such as population change over time.

Applications of Recurrence Relations

  • Practice problems set for tasks such as population growth, interest accumulation, and scheduling, demonstrating real-world scenarios where recurrence relations apply.
  • Example of population growth initiates with a given amount and growth percentage, establishing foundational computational methods.

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Explore key concepts and applications in Discrete Mathematics with these comprehensive lecture notes. Learn about logical relationships, sets, relations, and properties of numbers essential for problem-solving in the field. Perfect for students aiming to deepen their understanding of discrete structures and their practical applications.

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